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Selective separation property enhancement is quite important for membranes separations, especially for high mass ratio Mg2+/Li+ separations. Low selectivity and unclear separation mechanism are the challenges for current membranes. In this study, we designed 4-aminophenyl-15-crown-5 incorporated polyamide nanofiltration membranes through interfacial polymerization for Li+ enrichment. The electrochemical tests and energy barrier calculations using transition state theory confirmed that the crown ether in nanofiltration membrane is responsible for governing Mg2+ transportation, resulting in a substantial energy barrier impeding its transport. Furthermore, a two-stage nanofiltration process was employed to enhance Li+ enrichment in simulated brine and achieved 35-fold increase in Li+ enrichment using as-fabricated membranes. These results demonstrate the substantial potential for Li + extraction from brine with a high Mg2+/Li+ mass ratio using the crown ether incorporated membrane. Meanwhile, the proposed strategy incorporating transport barriers presents a novel approach for designing ion-selective channels within membranes. [Display omitted] • A novel crown ether nanofiltration polyamide membrane was fabricated by interfacial polymerization (IP) process. • PEI@4A-B15C5 membrane has a great hindrance to Mg2+ transport. • Efficient enrichment of Li+ from a simulated brine. [ABSTRACT FROM AUTHOR]

[Display omitted] • The unitary and binary pore CTF membranes were prepared by interfacial polymerization. • Ultrafast molecular-level perm-selectivity was finely tuned by the structural pore size. • The OSN membrane fouling could be alleviated via photocatalysis. • The membrane achieves multiple-cycle "operation-fouling-in situ cleaning-operation" stability for OSN process. Covalent organic frameworks (COF) membranes are considered as promising candidates for organic solvent nanofiltration (OSN) due to their well-defined porosity, high perm-selectivity, and exceptional resistance to solvents. However, irreversible membrane fouling caused by filter cake layers or pore clogging challenges the robust separation over long-term operation especially for well-known COF membranes. Here, we present novel ultrafast covalent triazine frameworks (CTF) membranes with retrievable separation performances for OSN processes. CTF-1 membrane with unitary nanopore and CTF-m membrane with binary nanopore are fabricated via an air-organic solvent interfacial polymerization technique for comparison, which demonstrates molecular-level selectivity (MWCO, ∼320 Da for CTF-1 and ∼ 625 Da for CTF-m) and ultrafast permeability for polar organic solvents. Moreover, the heterogeneous skeleton nanopores structure of CTF-m membranes facilitates efficient separation of photogenerated carriers, thus resulting in retrievable permselectivity. This work offers an efficient strategy via Donor-Acceptor structure modulation to tackle OSN membrane fouling, paving the way for applications of framework membranes. [ABSTRACT FROM AUTHOR]

[Display omitted] • We for the first time synthesize crystalline CTF-1 nanoribbons (CTF-1-NR). • The width of 1D nanoribbons can be facilely tuned by varying the solvent volume. • The CTF-1-NR are intercalated with Graphene Oxide (GO) membranes to enlarge water transport. • CTF-1-NR enhance photocatalytic ability compared to 2D nanosheets counterparts. • CTF-1-NR/GO membrane allows for recoverable permeability by solar illumination. Covalent triazine frameworks (CTFs) are drawing substantial interest as porous crystalline two-dimensional (2D) or three-dimensional (3D) nanomaterials. Fabrication of CTFs nanoribbon is challenging but appealing to separation and photocatalysis. Here we for the first time report the synthesis of crystalline CTF-1 nanoribbons (CTF-1-NR) comprising 2–3 covalent triazine framework units in width through a polar solvent-induced fragmentation strategy. The width of 1D nanoribbons can be facilely tuned by varying the solvent (e.g. ethanol) volume in trifluoromethanesulfonic acid layer after trimerization of aromatic nitriles. The CTF-1-NR are intercalated with Graphene oxide (GO) membranes to extend 1H NMR transverse relaxation time (T 2) and enlarge the confined interspacing (∼8.8 Å), providing ultrafast water transport (∼60 L m-2h−1 bar−1) and high dye molecules rejection (98%). More significantly, the bridging CTF-1-NR enhances charge-carrier separation and gains superior solar-cleaning recoverable permeability (∼7 folds higher than GO). This study provides novel insight into the synthesis of crystalline COF nanoribbons and membrane separation. [ABSTRACT FROM AUTHOR]

Photo-assisted catalysis is proposed to be an effective approach to deal with the membrane fouling issue, which restricts the broad application of burgeoning 2D covalent organic frameworks (COF) membranes in sustainable separation process. In this work, a new type of [0D + 2D] composite membrane was developed via covalent triazine frameworks (CTF-1) nanosheets with built-in CdS quantum dots (QDs). The regular skeleton of 2D-CTF-1 facilitated the uniform growth of CdS QDs (3 nm) on the planar nanosheets. CdS/CTF-1 composite membrane exhibits high water flux (>170 L m−2 h−1, 0.1 MPa) and high dyes rejection (>94%) via manipulating transportation channels. More importantly, the built-in [0D + 2D]-heterojunction significantly improves the photocatalytic in - situ cleaning and disinfection performance of CdS/CTF-1 membrane, allowing for regenerating permeability (>95%) with the assist of H 2 O 2 during multiple operations. Thus, we provide a prospective strategy to resolve the membrane fouling issues and enable the practical application of 2D membranes for continuous separation. Photocatalytic in - situ cleaning CdS/CTF-1 composite membrane achieves efficient and continuous separation. [Display omitted] • We literally resolve the fouling issue of 2D COF membranes for sustainable separation. • A novel [0D + 2D] membrane was developed by embedding CdS QDs in CTF-1 nanosheets. • CdS/CTF-1 membrane shows improved permeability due to additional channels. • CdS QDs enhance the photocatalytic in - situ cleaning and disinfection performance. • CdS/CTF-1 membrane regenerates its permeability >95% via sunlight illumination. [ABSTRACT FROM AUTHOR]

Photo-assisted catalysis is proposed to be an effective approach to deal with the membrane fouling issue, which restricts the broad application of burgeoning 2D covalent organic frameworks (COF) membranes in sustainable separation process. In this work, a new type of [0D + 2D] composite membrane was developed via covalent triazine frameworks (CTF-1) nanosheets with built-in CdS quantum dots (QDs). The regular skeleton of 2D-CTF-1 facilitated the uniform growth of CdS QDs (3 nm) on the planar nanosheets. CdS/CTF-1 composite membrane exhibits high water flux (>170 L m−2 h−1, 0.1 MPa) and high dyes rejection (>94%) via manipulating transportation channels. More importantly, the built-in [0D + 2D]-heterojunction significantly improves the photocatalytic in - situ cleaning and disinfection performance of CdS/CTF-1 membrane, allowing for regenerating permeability (>95%) with the assist of H 2 O 2 during multiple operations. Thus, we provide a prospective strategy to resolve the membrane fouling issues and enable the practical application of 2D membranes for continuous separation. Photocatalytic in - situ cleaning CdS/CTF-1 composite membrane achieves efficient and continuous separation. [Display omitted] • We literally resolve the fouling issue of 2D COF membranes for sustainable separation. • A novel [0D + 2D] membrane was developed by embedding CdS QDs in CTF-1 nanosheets. • CdS/CTF-1 membrane shows improved permeability due to additional channels. • CdS QDs enhance the photocatalytic in - situ cleaning and disinfection performance. • CdS/CTF-1 membrane regenerates its permeability >95% via sunlight illumination. [ABSTRACT FROM AUTHOR]

Two dimensional covalent triazine frameworks (2D-CTF) with controlled pore size and stable structure are a new class of 2D building blocks for constructing separation membrane materials. In this work, we synthesize few-layer 2D-CTF-1 nanosheets with high crystallinity and excellent solvent dispersion using a micro-interface method. The as-prepared 2D-CTF-1 membrane via filtration assembly of few-layer 2D-CTF-1 nanosheets exhibits superior permeability due to its ultralow solvent-interface interaction and the abundant in-plane pores, with a water permeance of 141.5 L m−2 h−1 at 1 bar. The skeleton-pores are proved to be the main transfer channels on 2D-CTF-1 membrane, which are stable and nondeformable by external pressure. Size screening based on the cut-off of skeleton-pore (1.39 nm) is also demonstrated, which enables 2D-CTF-1 membrane a huge application potential in precise molecule/ion sieving. Besides, a stable layered structure in aqueous environment renders 2D-CTF-1 membrane with outstanding separation performance in the long-term running, continuously keeping high permeability and selectively. Thus, this work shows a promising application of 2D-CTF-1 as building blocks for 2D membrane construction in the separation field. 2D-CTF-1 membrane with highly ordered skeleton nanopores (intrasheet pathways) as the main transfer channels exhibits robust and precise molecule/ion separation performance. Image 1 • Covalent triazine frameworks membranes were fabricated for precise separation. • The abundant skeleton-pores dominated the mass transfer of 2D-CTF-1 membrane. • Precise molecule sieving was achieved via the skeleton-pores at nano-scale. • 2D-CTF-1 membrane showed stable layered structure and separation performance. [ABSTRACT FROM AUTHOR]